This application claims priority to and the benefit of Korea Patent Application No. 2002-32907 filed on Jun. 12, 2002 in the Korean Intellectual Property Office, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus and a method for driving a plasma display panel.
2. Background of the Related Art
A plasma display panel is a kind of display device that selectively excites a plurality of discharge tubes arranged in a matrix form to reproduce video data inputted in the form of an electric signal. Methods of driving the plasma display panel are divided into DC and AC driving modes, according to whether the polarity of voltage applied to maintain discharge is varied with time or not.
In a plasma display panel of a three-electrode lateral discharge structure, address electrodes are arranged intersecting two parallel display electrodes, a scan electrode and a common electrode, in a discharge space formed by barriers. In this structure, discharging for generating wall charges occurs between the address electrodes and the scan electrode in order to select a pixel, and then discharging for displaying an image is repeated for a predetermined period of time between the scan electrode and the common electrode. The barriers not only form the discharge space but also shield light generated when discharge occurs to prevent crosstalk between neighboring pixels. A plurality of unit structures obtained as above is formed on a substrate in a matrix form, and a fluorescent material is coated on each unit structure to construct one pixel. A plurality of pixels formed in this manner construct a plasma display panel. A commercially available current plasma display panel is constructed in such a manner that discharging occurs in each pixel and ultraviolet rays generated according to the discharge excite fluorescent material coated on the inner wall of each pixel to produce a desired color.
In the driving of this AC plasma display panel that is a capacitive load, charging/discharging operations are carried out for all sustain pulses. During the charging/discharging operations, the common electrode and the scan electrode on the upper substrate of the display panel generate a lateral discharge. Before discharging, displacement current must be supplied to the panel that is a capacitive load because sustain occurs only after the displacement current is applied to the panel to charge the panel. In the case of a 42xe2x80x3 panel among commercially available products, approximately 2000 sustain pulses are applied over 16.67 ms. Even if a discharge current does not flow whenever all of these sustain pulses are applied, the displacement current must be supplied to the panel. The quantity of displacement current depends on an intrinsic capacitance that varies according to the shape or the material of each pixel, and consumption of ineffective power caused by this capacitance is considerable.
To solve this problem, a variety of methods for reducing the ineffective power have been studied. FIG. 1 shows a power recovery circuit for reducing the ineffective power.
In FIG. 1, switches Y1, Y2, Y3, and Y4, external capacitor C1, inductor L1, and diodes D1 and D2 construct a scan electrode driver, and switches X1, X2, X3, and X4, external capacitor C2, inductor L2, and diodes D3 and D4 construct a common electrode driver. In this configuration, serial resonance occurs between external capacitor C2 and inductor L2 during ON time of switch X1 so that the potential of a common electrode X increases to sustain voltage Vs when the resonance is completed. At this time, switch X2 is turned on to perform sustain. At the falling edge of a sustain pulse, switch X3 is turned on to create serial resonance between a panel capacitor Cp and inductor L2 to recharge external capacitor C2. When the resonance is completed, the potential of the common electrode X becomes identical to the ground voltage. At this time, switch X4 is turned on to maintain the ground voltage.
The aforementioned timing describes an ideal case, and actual timing takes into consideration of delay of drive ICs of FETs. The power recovery operation is executed for all sustain pulses of X and Y electrodes to minimize power consumption of the panel. This conventional power recovery circuit uses an independent circuit for each of the X and Y electrodes to increase the number of capacitors and inductors which results in inefficient operation of each circuit.
In accordance with the present invention consumption of ineffective power used in a plasma display panel is reduced. Circuits respectively used for a scan electrode and a common electrode are integrated into one circuit to simplify a process of fabricating a plasma display panel driver, reduce the number of capacitors and inductors, and effectively recover power.
In an aspect of the present invention, there is provided an apparatus for driving a plasma display panel including a plurality of scan electrodes and common electrodes arranged in pairs and a panel capacitor formed between each scan electrode and common electrode. The apparatus has a sustain part including first and second switches that are coupled in series between a first voltage and a second voltage, and third and fourth switches that are coupled in series between the first voltage and the second voltage. A coupling node of the first and second switches is coupled to one end of the panel capacitor. A coupling node of the third and fourth switches is coupled to the other end of the panel capacitor. The sustain part maintains the voltage of one end of the panel capacitor and the voltage of the other end of the panel capacitor at the first or second voltage. A charging/discharging part includes an inductor with one end coupled to the coupling node of the first and second switches and the coupling node of the third and fourth switches through first and second paths, respectively, and an external capacitor coupled between the other end of the inductor and the second voltage through third and fourth paths, the charging/discharging part charging the voltage of one end of the panel capacitor and voltage of the other end thereof with the first voltage or discharging them to the second voltage.
The apparatus for driving a plasma display panel of the invention can further include fifth and sixth switches that are coupled between the panel capacitor and the inductor through the first and second paths, respectively, to select a path of current flowing through the panel capacitor from the first and second paths.
The apparatus for driving a plasma display panel of the invention can further include a seventh switch and a first diode that are placed on the third path to set a path of current supplied to the panel capacitor, and an eighth switch and a second diode that are located on the fourth path to set a path of current recovered from the panel capacitor.
In another aspect of the present invention, there is also provided a method for driving a plasma display panel having a panel capacitor with both ends supplied with first and second voltages alternately, an external capacitor supplied with a voltage corresponding to the middle level between the first and second voltages, and an inductor coupled to the external capacitor. The voltage of one end of the panel capacitor is charged up to the first voltage using resonance that is generated when the inductor is coupled to one end of the panel capacitor through a first path. The voltage of one end of the panel capacitor is discharged to the second voltage using resonance that occurs when the inductor is coupled to one end of the panel capacitor through the first path. The voltage of the other end of the panel capacitor is charged up to the first voltage using resonance that is generated when the inductor is coupled to the other end of the panel capacitor through a second path. The voltage of the other end of the panel capacitor is discharged to the second voltage using resonance generated when the inductor is coupled to the other end of the panel capacitor through the second path.
The charging of the voltage of one end of the panel capacitor can include maintaining the voltage of one end of the panel capacitor at the first voltage using first and second switches, which are coupled in series between the first voltage and the second voltage, and third and fourth switches, which are coupled in series between the first voltage and the second voltage. A coupling node of the first and second switches is coupled to one end of the panel capacitor. A coupling node of the third and fourth switches is coupled to the other end of the panel capacitor. The charging of the voltage of the other end of the panel capacitor can include maintaining the voltage of the other end of the panel capacitor at the first voltage using the first, second, third, and fourth switches.
The method for driving a plasma display panel according to the present invention can select a path of current flowing through the panel capacitor from the first and second paths using fifth and sixth switches that are respectively coupled to the first and second paths.
Each of the switches used in the apparatus and method for driving a plasma display panel of the invention can have a body diode.
In another aspect of the present invention, there is also provided an apparatus for driving a plasma display panel including a first electrode and a second electrode, and a panel capacitor formed between the first electrode and the second electrode. The apparatus includes a power source supplying a first voltage, an inductor, a first current path formed from the power source to the first electrode via the inductor to generate a resonance between the panel capacitor and the inductor, thereby changing the voltage of the first electrode to a second voltage, while the voltage of the second electrode is maintained to a third voltage. A second current path is formed from the first electrode to the power source via the inductor to generate a resonance between the panel capacitor and the inductor, thereby changing the voltage of the first electrode to the third voltage, while the voltage of the second electrode is maintained to the third voltage. A third current path is formed from the power source to the second electrode via the inductor to generate a resonance between the panel capacitor and the inductor, thereby changing the voltage of the second electrode to the second voltage, while the voltage of the first electrode is maintained to the third voltage. A fourth current path is formed from the second electrode to the power source via the inductor to generate a resonance between the panel capacitor and the inductor, thereby changing the voltage of the second electrode to the third voltage, while the voltage of the first electrode is maintained to the third voltage.